Heat processing of canned foodstuffs

ABSTRACT

An apparatus for heat-processing canned foodstuffs has a gasfluidised heating bed optionally followed by one or more gasfluidised cooling beds. The cans are fed downward through the heating bed so as to subject them to a progressively increasing external pressure which compensates for rises in their internal pressure as they are heated.

United States Patent [191 Jowitt et al.

[ Aug. 28, 1973 HEAT PROCESSING OF CANNED FOODSTUFFS Inventors: Ronald Jowitt, Kent, Beckenham;

Stuart Nigel Thome, Cambridge, both of England National Research Development Corporation, London, England F iled: Feb. 26, 1971 Appl. No.: 119,310

Assignee:

Foreign Application Priority Data Feb. 27, 1970 Great Britain 9,727/70 US. Cl 99/361, 99/367, 99/214 Int. Cl A23b 3/02 Field of Search 99/249, 251, 360,

References Cited UNITED STATES PATENTS 8/1952 Martin 99/249 6/1953 Bingham.... 99/361 11/1971 Carvallo 99/249 Primary Examiner-Robert W. Jenkins AttorneyCushman, Darby & Cushman [5 7] ABSTRACT 7 Claims, 3 Drawing Figures PATENTEDmsze Ian 3.754.467

' sum 1 OF 3 v PATENTED AUG 28 I975 SHEEI 2 BF 3 PATENIEUwsza 1915 SHEET 3 0F 3 K E J HEAT PROCESSING OF CANNED FOODSTUFFS The present invention relates to the canning of foodstuffs.

Many foodstuffs can be preserved for long periods by heating them in sealed containers to destroy microorganisms present in the food. Hitherto the cans have been heated in steam or pressurised water in batch or continuous coolers and cooled by immersion in or spraying with cold water.

According to one aspect of the present invention, an apparatus for heat-processing canned foodstuffs comprises means for producing a gas-fluidised heating bed and feeder means adapted progressively to increase the immersion of a can of the foodstuff in the gas-fluidised heating bed.

In one embodiment, the feeder means is adapted to move the can from end to end of successive vertically aligned paths in the heating bed. Thus the feeder means may comprise a plurality of vertically separated pusher bars mounted for oscillatory movement longitudinally of the bars and transport means adapted to move cans from the end of one pusher bar to the adjacent end to an adjacent pusher bar, and drive means arranged to operate said transport mechanism in predetermined relationship with said oscillating pusher bars.

The apparatus may also include a cooling system and transfer means for transferring cans from the heating bed to the cooling system. The cooling system may comprise means for producing one or more gasfluidised cooling beds for example. Conveniently in this case the tops of the heating and cooling beds are at atmospheric pressure, and the bottoms of the heating bed and of the following cooling bed are maintained at the same pressure so that the heated can may be passed directly from the heating bed to the lower (high pressure) end of said following cooling bed. In this case a feeder means may be provided which is adapted progressively to decrease the immersion of the can in said following cooling bed.

In a preferred embodiment, the cooling system comprises at least two gas-fluidised cooling beds, transfer means for transferring the can from the top of the first cooling bed to the top of the second cooling bed, and feeder means adapted to pass the can through the second cooling bed. The first cooling bed is preferably adapted to remove most of the heat from the heated cans of foodstuff and in one embodiment the first cooling bed is adapted to cool the cans of foodstuff to about one third of the temperature in F to which they have been previously heated by the heating bed. Thus the invention includes one such apparatus in which the gasfluidised heating bed is at about 250F, the first cooling bed is at about 90F and the second cooling bed is at about 75F. Typically in this case for a 17 ounce can of meat product for example the feeder mechanisms would be adapted to give residence times of 60 minutes in the heating bed, 60 minutes in the first cooling bed and 40 minutes in the second cooling bed.

According to another aspect of the invention, a method of heat-processing canned foodstuff by immersion of a can of the foodstuff in a gas-fluidised heating bed includes the step of progressively increasing the immersion of the can in the heating bed thereby to increase the pressure exerted by the heating bed on the outside of the can to compensate for pressure increase occurring in the can during heating, and thereafter cooling the can.

The invention also includes a foodstuff or a can of foodstuff heated by the apparatus and/or the method of the present invention.

It should be pointed out that whereas the pressure in the bed increases in roughly linear fashion with depth, the internal pressure in the cans increases in a nonlinear fashion with increasing immersion of the cans in the bed so that whilst the pressure acting on the outsides of the cans tends to over-compensate for the corresponding pressure rises inside the cans during the early stages of heating, during the critical late stages of the process, the two pressures are very nearly equilibrated. This situation ensures that there is a negligible possibility of the cans bursting during heating.

In the preferred embodiment using a gas-fluidised cooling bed after the heating bed, the external pressure in the cooling bed initially equilibrates the internal pressure in the cans, and later in the process, the external pressure over-compensates for the internal pressure, thus reducing to negligible proportions the chance of either the cans bursting during cooling or contamination by bacteria entering the cans through the seams. In addition, high cooling rates are achieved without cooling water touching the cans, thereby avoiding the risks associated with potentially nonsterile water being drawn into the cans because these are improperly sealed or temporarily distorted or because the sealing members are in a plastic condition when the cans are removed from the heating bed. Pressure sealing problems associated with conventional heat processing plants can also be eliminated by having the tops of the beds at atmospheric pressure, and the bottom of the heating bed and of the following cooling bed at the same pressure.

The preferred feature of using a multi-stage fluidisedbed cooling system as opposed to cooling with a single fluidised-bed also produces advantages when compared with a corresponding fluidised-bed heat processing apparatus using only one fluidised-bed cooling stage. Thus cooling times in a single bed would be long because of the small temperature difference between the cans and the beds, and the small temperature differences between the bed and cooling water. Reducing the bed operating temperature would increase the temperature difference between the bed and cans in such an instance but would also reduce the temperature difference between the bed and the cooling water, necessitating increased cooling water throughputs or heat exchange areas. Conversely, raising the bed operating temperature in a single-stage cooler would mean longer residence times. With the two-stage cooler of the present invention, however, the first bed preferably removes most of the heat with large temperature differences between the cooling water and the bed and the second bed operates at a low temperature to cool the cans of food to F or less. Thus with the two-stage cooler system of the present invention, either residence times of the cans of food in the cooler system can be reduced or the quantity of cooler water required can be reduced as compared with a single-stage cooler.

Another advantage of the two-stage cooler system is that pressure need only be applied to the outside of the can of foodstufi' during cooling until the can centre has cooled to about 220F. Thus the second cooler need not have to exert a pressure on the cans and as a consever sand, with a consequent reduction in the quantity of fluidising gas required.

The term gas-fluidised bed as used herein means a bed of solid particles supported by a gas flow such that the bed is able to permit the passage of solid objects, e.g. the cans of foodstuff, immersed, or partially so, in the bed.

In order that the invention may be more fully understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawing, of which:

FIG. 1 shows a heat processing apparatus in accordance with the present invention; and

FIG. 2 shows a feeder mechanism for use in the apparatus of FIG. 1.

Referring first to FIG. 1, a heat processing apparatus according to the present invention comprises a gasfluidised bed heater in which cans of the foodstuff can be heated to a sufficiently high temperature to destroy micro-organisms present in the foodstuff. This is followed by a first fluidised bed cooler 12 for removing most of the heat from the cans of foodstuff, and a second fluidised bed cooler 14 for further cooling of the cans of foodstuff.

As above described, the pressure in the fluidised heating bed increases with depth and to utilise the invention to the full, the flow rate of the suspending gas and the specific gravity of the particles are chosen to provide a range of pressures in the heating bed especially suited to the cans of foodstuff under treatment.

The illustrated apparatus utilises a typical heating bed in accordance with the present invention designed for heating cans of a meat product with a weight of 17 ounces and external volume of 33 cubic inches. In this bed, the pressure varies in a roughly linear fashion from a maximum of 15 lbs. per square inch above atmospheric pressure at the bottom of the bed to a minimum of atmospheric pressure at the top. This is achieved by suspending particles of magnetite (or haematite) with a maximum dimension of say 0.02 inches and a specific gravity of 5.2 in an upward flow of hot gas (flow rate of 85 lbs. per square foot of bed per hour to a bed depth of 16 feet. A roots blower 26 operating at 4 X 10 lb./hour at 15 p.s.i.g. drives air into a dilution chamber 24 and a combustion chamber 22 to which an oil fuel is pumped by ful pump fuel at the rate of 43 lb./hour. The mixture of air and combustion products enter the lower end of heater 10 at a temperature of I420F and discharge from the upper end at a temperature of 250F. It then passes through piping 32 to a cyclone separator 33 where solid particles in the gas are separated out.

An inlet conveyor mechanism 42 feeds cans into the upper end of heater 10 at a rate of 200 cans/min. These cans have been hot filled at a temperature of I50F before entering the heater. The residence time of each can in the heater will depend on the size of the can and the nature of its contents, but with the 17 ounce cans above described, each can is typically immersed in the bed for about 60 minutes during which time its depth of immersion is increased in horizontal passes across the bed to a maximum of about 15 foot immersion. During this time, the internal pressure in the can is raised from an initial value of around 6 lbs. per square inch below atmospheric pressure to a final value of around 15 lbs. per square inch above atmospheric pressure. On reaching the lower end of the heater 10, the cans are discharged on to a conveyor mechanism 46 which feeds them to the lower end of the first cooling bed 12.

The feed mechanism 44 for moving the cans through heater 10 comprises a plurality of pusher bars of which the upper two bars 60A, 60B, are shown in detail in FIG. 2. These bars are vertically aligned with one another over the height of the heater (and coolers) and operate to move the cans from end to end of a series of vertically aligned horizontal paths 62 indicated diagrammatically in FIG. 1.

As shown in FIG. 2, each pusher bar has a number of upwardly and downwardly extending protrusions or pegs 64 spaced apart from one another by an amount somewhat greater than the diameter of the cans of which 12 (A L) are shown. The cans are located between pairs of rails or tracks 66 which define the can paths above referred to. The vertical separation of the tracks is such that the pegs 64 can be located between the cans of only one track at a time. Each of the bars 60A, 60B etc. is mounted so as to be capable of a limited degree of upward movement (so it can engage with the cans on the upwardly adjacent track), downward movement (so it can engage with the cans on the downwardly adjacent track), and sideward movement so it can move each can to the position on its track previously occupied by the adjacent can on that track. Can register bars (such as bar 65) are positioned between adjacent pusher bars 60A, 608 etc. The register bars are similar to the pusher bars in their construction and their facility for vertical movement but they are not free to move sidewards. Their purpose is to locate the cans when these are not engaged by the pegs of the pusher bars.

The feed mechanism is completed by vertical transport mechanisms (such as mechanisms 68, 69) which have upper and lower In an alternative arms (for engaging the cans) slotted to permit pegs 66 to traverse the transport mechanism, (as indicated at position 64' for example).

In more detail the pusher bars A, 603 etc. and the register bars etc. are rigidly connected between shafts 70, 71 mounted to be driven in a vertical oscilla tory movement by hydraulic rams 72, 73. The pusher bars are also arranged to be driven in an oscillatory side-to-side motion by hydraulic rams such as ram 74 which is connected to shaft 71 through lost motion mechanisms 75, 76. The vertical transfer mechanisms (such as mechanism 68) on one side of the pusher bars are driven from a common shaft 77 associated with a hydraulic ram 78 whilst those on the other side of the pusher bars (such as mechanism 69) are driven from a common shaft 79 associated with another hydraulic ram 80. Inalternative embodiment, the various hydraulic rams above referred to may be replaced by pneumatic rams.

Typically, rams 72, 73 will have a complete stroke length of about 3 inches (i.e. 1% inches in either direction), whilst ram 74 has a complete stroke of about 3 V4 inches.

It will be appreciated from the above description, that the pusher bars 60A, 60B will move in a closed rectangular path, the register bars such as bar 65 will execute the same vertical movements as the pusher bars do in moving over this closed path, and the vertical transport mechamisms 68, 69 will execute a vertical oscillatory movement between adjacent rows of pusher bars.

The operating fluid for the various rams is controlled by a valve assembly (not shown) which is operated by a series of adjustable cams mounted on a common shaft which is arranged to be driven by a constant speed motor.

Taking the operation of the feeder means from the situations illustrated in FIG. 2, ram 78 is actuated to move the transport mechanisms on the right hand side of the bed up one row. Thus, transport mechanism 68 moves to new position 68 and the next transport mechanism on that side moves into position 82'.

Rams 72, 73 are then operated to move the pusher bars 60A, 60B etc. and the register bars 60' etc. down one stroke so that the pegs 64 on these bars engage between the cans in the rows beneath the bars. Ram 74 is now operated to drive the pusher bars to the right and move the cans in the 1st, 3rd, 5th rows etc. (e.g. cans A to E and I to L) one position to the right, the end cans (e.g. cans E, L) being moved into the vertical transport mechanisms at 68 82' (as indicated at E and L). A new can (A') rolls from an inlet chute 84 into the position perviously occupied by can A.

Rams 78 and 80 are now operated to drive the transport mechanisms 68 etc. down one row (mechanism 68 thereby returning to its illustrated position) and the transport mechanisms 69 etc. up one row.

Rams 72, 73 next operate to drive the pusher bars and register bars up one stroke to engage the pegs 64 between the cans of the rows above these bars. Ram 74 is now operated to move the cans in the 2nd, 4th, 6th rows etc. (e.g. cans E to H) one place to the left, the end cans (e.g. can H) moving into the appropriate transport mechanism (e.g. mechanism 69) on the left side of the bed. Finally ram 80 is operated to drive transfer means 69 etc. down one stroke and move these end cans to the row below, thereby returning mechanism 69 to its illustrated position. Thus can H, for example, will be moved from position H to the position previously occupied by can I.

The feeder mechanism will now have returned to the situation illustrated in FIG. 2 except that the can A is in place of can A, can A is in place of can B, can-B is in place of can C etc. The above described operation is then repeated for the newly positioned cans, the endmost can of the bottom row of the assembly being fed out on to the transfer mechanism 46 (FIG. 1) each time a new can is accepted from the inlet chute 84.

Although for convenience the cans in the various rows have been identified by using successive letters of the alphabet, it will of course be understood that cans D, H and K do not immediately follow cans C, G and J, the total number of cans in each row being in fact typically 30 cans.

In the cooler 12 the solid particles are again of magnctite (or haematite) and they are suspended in a gas flow provided by Roots blower 28, operating at 2,600 lb.lhour, p.s.i.g. In cooler 14 there is no need to apply pressure to the cans and hence a relatively low density material can be used e.g. silver sand of maximum particle size 0.02 inches. This is suspended by Roots blower 30 operating'at 800 lb.lhour, 4 p.s.i.g. Gas discharged from the two coolers is fed by piping 32 to the cyclone separator 33 where solid particles in the discharged gas are separated out.

Cooling of the fluidised beds in the two coolers is effected by respective heat exchange systems 34, 36 fed with cooling water at an inlet temperature of 60F by pumps 38, 40 operating at 825 lb.lmin. and 346 lb.lmin. respectively. Water discharged from the heat exchange system of cooler 12 will have been raised to a temperature of F during its passage through the cooler whilst that from cooler 14 will be discharged at a temperature of 75F.

The cans are moved through cooler 12 (residence time roughly 60 minutes, say) by a feed mechanism in the cooler 12 to the top end of the cooler where they are discharged on to a conveyor mechanism which feeds them into the upper end of the second cooler 14. A feed mechanism in the cooler [4 moves the cans to the bottom end of cooler 14 and then back to the upper end of cooler 14 where they are discharged on to an exit conveyor mechanism 50 at a temperature of about 100F. The residence time of the cans in cooler 14 will be roughly 40 minutes say. The feeder mechanism for bed 12 is substantially identical to the corresponding mechanism 44 of heater 10 but the control cams are adjusted to operate the rams in the reverse sequence so that the cans are fed upwardly through the bed instead. The feed mechanism for cooler 14 comprises two such mechanisms in series, one operated as in heater 10 to feed the cans to the bottom of cooler 14 and the other operated as in cooler 12 to return the cans to the top of cooler 14. A transfer means is provided in the cooler 14 to transfer the cans from the bottom of the one mechamism to the bottom of the other. The cans are finally discharged by mechanism 50 to an appropriate store place for cooling to ambient temperature.

With conventional heat processing plants for canned foodstuffs, the cans have to be removed in the region of to F so that any water on the can surface will evaporate rapidly before stacking. This has the disadvantage that if the cans are stacked on pallets (as is normal practice), those in the middle of the stack may retain this temperature for sufficient time to allow thermophyllic organisms which may be present in the foodstuff to grow.

It is an advantage of the present invention that there is no fundamental reason why the apparatus should not be operated so that the cans can be discharged at a smaller temperature e.g. 80F or so, since there is no water used in the process which could require evaporation from the can surfaces. It follows that the cans can be stacked in the usual way with a significantly lessened danger of any therrnophyllic organisms present growmg.

Thus according to another aspect of the invention, the apparatus above described with reference to FIGS. 1 and 2 could be operated with the cans entering heater 10 at 80F say and leaving at 245F. The first cooler (12) is operated at a bed temperature of 90F and is cooled by cooling water entering the heat exchanger at 60F and leaving at 80F with a flow rate of 950 lbs/min. The cans leave the first cooler at a temperature of F after a residence time there of 60 minutes. They then enter the second cooler which is operated at a bed temperature of 75F by a flow of cooling water entering the heat exchanger at 60F and leaving at 75F (water flow rate, 500 lbs./min.). The residence time of the cans in the second cooling bed is 60 minutes and during this time they are cooled from their initial temperature of 120F to a discharge temperature of about 80F.

In one variation of the apparatus shown in FIGS. 1 and 2, all or some of the feed mechanisms 44 in the heater and the two coolers are replaced by one using pallets or wire baskets (in which cans of varying sizes can be mounted) passing from end to end of the bed concerned.

In another variation, the heat exchangers 36, 34 are connected in series, the water discharged from heat exchanger 36 being used as feed water for heat exchanger 34.

The conveyor mechanisms 42,46,48 and 50 in FIG. 1 of the drawings may, for example, comprise conveyor belts having spaced pegs similar to those of feed mechanism 44 in FIG. 2. Guide rails (similar to rails 66) may also be provided.

We claim:

1. An apparatus for heat processing canned foodstuffs, the apparatus comprising a heating chamber, means adapted to produce in said chamber a gas fluidised heating bed, constituted by a bed of solid particles supported by a gas flow such that the bed is able to permit passage of cans of foodstuff at least partially immersed therein an inlet for introducing cans of the foodstuff into an upper region of said chamber an outlet for removing the cans from a lower region of said chamber, feeder means for the cans having canengaging surfaces, and drive means adapted to move said can-engaging surfaces to feed the cans from said upper region to said lower region.

2. An apparatus as claimed in claim 1 including a first cooling chamber, means adapted to produce in said first cooling chamber a gas fluidised cooling bed adapted to remove most of the heat from the heated cans of foodstuff, a second cooling chamber, and means adapted to produce in said second cooling chamber a second gas fluidised cooling bed further to cool said cans.

3. An apparatus as claimed in claim 2 comprising inlets for introducing cans of foodstuff to a lower region of the first cooling bed chamber and an upper region of the second cooling bed chamber, outlets for removing the cans from an upper region of the first cooling bed chamber and from a lower region of the second cooling bed chamber, feeder means for the cans in the two cooling chambers, can-engaging surfaces to said feeder means, drive means adapted to move said canengaging surfaces from the regions having said inlets to the region having said outlets, and transfer means for moving the cans from the lower region of the heating chamber to the lower region of the first cooling chamber and from the upper region of the first cooling chamber to the upper region of the second cooling chamber.

4. An apparatus as claimed in claim 3 wherein said feeder means for the heating chamber comprises a plurality of vertically separated pusher bars mounted for oscillatory movement longitudinally of the bars, and transport means adapted to move cans from the end of one pusher bar to the adjacent end to the sub-adjacent bar,

5. An apparatus as claimed in claim 3 in which the first cooling bed is adapted to cool the cans of foodstuff to about one third of the temperature in F to which they have been previously heated by the heating bed.

6. An apparatus as claimed in claim 5 in which the heating means comprises a gas-fluidised heating bed adapted to heat cans of foodstuff to a temperature of about 250F, the first cooling bed is adapted to cool the cans of foodstuff to a temperature of about 90F and the second cooling bed is adapted to cool the cans of foodstuff to a temperature of about F.

7. An apparatus for heat processing canned foodstuffs, the apparatus comprising:

means defining a heating chamber;

a body of solid, particulate fluidizable media partly filling said heating chamber;

fluidization gas conduit means communicating to and from said chamber for directing sufficient gas upwardly through the body to produce a fluidized bed thereof partly filling said heating chamber and being of sufficiently low density to permit the submergence of cans therein;

inlet means to said chamber above the upper level of the fluidized bed for introducing cans to said chamber;

outlet means from said chamber substantially below the upper level of the fluidized bed;

feeder means for the cans introduced to said chamber, said feeder means including can-engaging surfaces, and

drive means for progressively moving said can engaging surfaces through a path from above the upper level of the fluidized bed to substantially below the upper level of the fluidized bed for forwarding cans introduced to said chamber through said inlet means into the fluidized bed and toward said outlet means for transfer from said chamber through said outlet means. 

1. An apparatus for heat processing canned foodstuffs, the apparatus comprising a heating chamber, means adapted to produce in said chamber a gas fluidised heating bed, constituted by a bed of solid particles supported by a gas flow such that the bed is able to permit passage of cans of foodstuff at least partially immersed therein an inlet for introducing cans of the foodstuff into an upper region of said chamber an outlet for removing the cans from a lower region of said chamber, feeder means for the cans having can-engaging surfaces, and drive means adapted to move said can-engaging surfaces to feed the cans from said upper region to said lower region.
 2. An apparatus as claimed in claim 1 including a first cooling chamber, means adapted to produce in said first cooling chamber a gas fluidised cooling bed adapted to remove most of the heat from the heated cans of foodstuff, a second cooling chamber, and means adapted to produce in said second cooling chamber a second gas fluidised cooling bed further to cool said cans.
 3. An apparatus as claimed in claim 2 comprising inlets for introducing cans of foodstuff to a lower region of the first cooling bed chamber and an upper region of the second cooling bed chamber, outlets for removing the cans from an upper region of the first cooling bed chamber and from a lower region of the second cooling bed chamber, feeder means for the cans in the two cooling chambers, can-engaging surfaces to said feeder means, drive means adapted to move said can-engaging surfaces from the regions having said inlets to the region having said outlets, and transfer means for moving the cans from the lower region of the heating chamber to the lower region of the first cooling chamber and from the upper region of the first cooling chamber to the upper region of the second cooling chamber.
 4. An apparatus as claimed in claim 3 wherein said feeder means for the heating chamber comprises a plurality of vertically separated pusher bars mounted for oscillatory movement longitudinally of the bars, and transport means adapted to move cans from the end of one pusher bar to the adjacent end to the sub-adjacent bar.
 5. An apparatus as claimed in claim 3 in which the first cooling bed is adapted to cool the cans of foodstuff to about one third of the temperature in *F to which they have been previously heated by the heating bed.
 6. An apparatus as claimed in claim 5 in which the heating means comprises a gas-fluidised heating bed adapted to heat cans of foodstuff to a temperature of about 250*F, the first cooling bed is adapted to cool the cans of foodstuff to a temperature of about 90*F and the second cooling bed is adapted to cool the cans of foodstuff to a temperature of about 75*F.
 7. An apparatus for heat processing canned foodstuffs, the apparatus comprising: means defining a heating chamber; a body of solid, particulate fluidizable media partly filling said heating chamber; fluidization gas conduit means communicating to and from said chamber for directing sufficient gas upwardly through the body to produce a fluidized bed thereof partly filling said heating chamber and being of sufficiently low density to permit the submergence of cans therein; inlet means to said chamber above the upper level of the fluidized bed for introducing cans to said chamber; outlet means from said chamber substantially below the upper level of the fluidized bed; feeder means for the cans introduced to said chamber, said feeder means including can-engaging surfaces, and drive means for progressively moving said can engaging surfaces through a path from above the upper level of the fluidized bed to substantially below the upper level of the fluidized bed for forwarding cans introduced to said chamber through said inlet means into the fluidized bed and toward said outlet means for transfer from said chamber through said outlet means. 